History of Roman and Byzantine domes

Domes were a characteristic element of the architecture of Ancient Rome and of its medieval continuation, the Byzantine Empire. They had widespread influence on contemporary and later styles, from Russian and Ottoman architecture to the Italian Renaissance and modern revivals. The domes were customarily hemispherical, although octagonal and segmented shapes are also known, and they developed in form, use, and structure over the centuries. Early examples rested directly on the rotunda walls of round rooms and featured a central oculus for ventilation and light. Pendentives became common in the Byzantine period, provided support for domes over square spaces.

Early wooden domes are known only from a literary source, but the use of wooden formwork, concrete, and unskilled labor enabled domes of monumental size in the late Republic and early Imperial period, such as the so-called "Temple of Mercury" bath hall at Baiae. Nero introduced the dome into Roman palace architecture in the 1st century and such rooms served as state banqueting halls, audience rooms, or throne rooms. The Pantheon's dome, the largest and most famous example, was built of concrete in the 2nd century and may have served as an audience hall for Hadrian. Imperial mausolea, such as the Mausoleum of Diocletian, were domed beginning in the 3rd century. Some smaller domes were built with a technique of using ceramic tubes in place of a wooden centering for concrete, or as a permanent structure embedded in the concrete, but light brick became the preferred building material over the course of the 4th and 5th centuries. Brick ribs allowed for a thinner structure and facilitated the use of windows in the supporting walls, replacing the need for an oculus as a light source.

Christian baptisteries and shrines were domed in the 4th century, such as the Lateran Baptistery and the likely wooden dome over the Church of the Holy Sepulchre. Constantine's octagonal church in Antioch may have been a precedent for similar buildings for centuries afterward. The first domed basilica may have been built in the 5th century, with a church in southern Turkey being the earliest proposed example, but the 6th century architecture of Justinian made domed church architecture standard throughout the Roman east. His Hagia Sophia and Church of the Holy Apostles inspired copies in later centuries.

Cruciform churches with domes at their crossings, such as the churches of Hagia Sophia in Thessaloniki and St. Nicholas at Myra, were typical of 7th and 8th century architecture and bracing a dome with barrel vaults on four sides became the standard structural system. Domes over windowed drums of cylindrical or polygonal shape were standard after the 9th century. In the empire's later period, smaller churches were built with smaller diameter domes, normally less than 6 meters (20 ft) after the 10th century. Exceptions include the 11th century domed-octagons of Hosios Loukas and Nea Moni, and the 12th century Chora Church, among others. The cross-in-square plan, with a single dome at the crossing or five domes in a quincunx pattern, as at the Church of St. Panteleimon, was the most popular type from the 10th century until the fall of Constantinople in 1453.